#include <iostream>
using namespace std;
const int N = 25;
typedef long long LL;
LL f[N][N];
int n, m;
int x, y;
int dx[] = { 1,1,-1,-1,2,2,-2,-2 };
int dy[] = { 2,-2,2,-2,1,-1,1,-1 };

int main()
{
	cin >> n >> m;
	cin >> x >> y;
	f[x][y] = -1;
	for (int k = 0; k < 8; k++) {
		int a=x+dx[k],b=y+dy[k];
		if(a<0||b<0) continue;
		f[a][b] = -1;
	}

	for (int i = 0; i <= n; i++) {
		for (int j = 0; j <= m; j++) {
			if (i == 0 && j == 0) f[i][j] = 1;
			else if (f[i][j] == -1) f[i][j] = 0;
			else if (i - 1 < 0) f[i][j] = f[i][j - 1];
			else if (j - 1 < 0) f[i][j] = f[i - 1][j];
			else f[i][j] = f[i - 1][j] + f[i][j - 1];
		}
	}
	cout << f[n][m] << endl;

	return 0;
}
